Motor operated valve analysis and testing system

ABSTRACT

A valve analysis and testing system includes various devices for measuring the operating characteristics of a valve and its operator and the corresponding imposed valve stem load, which devices are attached to the valve operator. These devices provide for statically calibrating the operator relative to the imposed valve load and provide recording traces of the imposed load and associated parameters during dynamic conditions as related to the operation of the operator and valve combined. The system provides initial dynamic traces after initial assembly, maintenance and/or periodic testing of the operator and valve. The system is then used to provide diagnostic dynamic traces at any specified time in the future for the operator and valve. These future traces are used to compare with earlier traces to verify correct performance and most importantly to detect induced or impending damage, malfunctions, or maintenance requirements for the operator and valve.

This application is a continuation of application Ser. No. 515,358,filed July 19, 1983, now U.S. Pat. No. 4,542,649.

BACKGROUND OF THE INVENTION

This invention generally relates to a system by which the overallperformance and actual thrust loads delivered by an electromechanical,mechanical, pneumatic or hydraulic valve operator can be statically anddynamically monitored.

The conditions giving rise to the problems solved by this invention arecommonly found in industries utilizing externally driven valves. Inparticular within the power industry, valves are operated remotely fromopen, closed and intermediate positions to improve or maintain utilitypower plant output, or in many cases provide for the protection of plantequipment, as well as protection of the general public from release ofradioactive materials either directly or indirectly. Continual properoperation of these valves is essential to industries and the generalpublic.

Typically these valves are required to operate under differing operatingconditions of temperature, pressure and flow within the commonrequirement for consistent operation. Further, the inherent operatingcharacteristics of the valve and operator are constantly undergoingmechanical or electrical changes from maintenance, repair, adjustments,calibration and wear.

In the earlier state of the art, remote and local externally operatedvalves have been tested and calibrated to demonstrate that the operatorwill deliver the minimum or maximum thrust loads to the valve stem understatic conditions. The prior state of the art did not provideverification that the static load delivered by the operator wasacceptable after field assembly or maintenance, nor did the prior artprovide any verification of the imposed valve load under dynamicconditions.

Historically, the thrust required to open or shut and subsequently toseat a valve was determined analytically by considering such factors astemperature, pressure, pressure drop, flow, liquid, valve type, packingload, motor voltage and valve mechanical characteristics. Once theminimum and maximum valve thrust requirements were determinedanalytically, the valve operator size could then be selected. Normally,motor operated valves in nuclear power plants, which perform a safetyfunction, are required to operate between seventy-five and onehundred-ten percent (75-110%) of nominal line voltage applied to theoperator. This requirement could lead to sizing of operator motors whichcan deliver from 1.0 to 2.5 times the required valve stem thrust,depending upon the actual line voltage. With oversized motors andoperators, the load imposed on the valve is typically much larger thananticipated or estimated by static means, due to the inherentmotor/operator inertia effects. Prior state of the art methods forminimizing the effects of dynamic or inertia forces involved the use oftorque switches, motor brakes or compensating springs. Although thesedevices provided some relief, they do not preclude excessive orinadequate thrust loads being delivered to the valve stem, seat andbody. Complicating this situation is the fact that when a valve leaks,common practice has been to increase the force delivered to the valvestem through increased torque switch adjustments. Studies have shownthat this approach subsequently leads in many cases to irrevocabledamage to the valve or inoperativeness and more importantly degradationof system reliability as a whole.

The basic shortcoming of the prior art-load limiting devices is thatthey are not diagnostic in nature and, as in the the case of the torqueswitch, provide an element of protection which does not take intoaccount the dynamic considerations of the valve and operator duringactual operation. Changing effects on valve load under dynamicconditions such as line voltage, packing tightness, gear train wear,lubrication degradation, calibration, and adjustment errors cannot beidentified with the earlier state of the art devices. Further, in mostcases, prior state of the art post-maintenance valve and operatoractuation testing will not identify progressive degradation of valveperformance.

A SUMMARY OF THE INVENTION

Briefly described, the present invention comprises a modification to theprior state of the art, which includes the addition of a device(s) whichwill measure motion of the operator drive system continuously andprovide a dynamic trace of the actual load being delivered to the valvethroughout the operation cycle. After initial calibration, the recordedtrace will provide accurate information upon which more accurate andappropriate load limiting device adjustments can be made. In doing so,increased system reliability and reduced probability of physical valvedamage can be obtained. This improvement over the state of the art alsoprovides a means to determine, monitor and test valve and operatorperformance throughout its cycle, from open to closed positions and viceversa. Information on valve performance, which heretofore, wasunavailable from the previous state of the art protection devices, willprovide a direct indication of developing valve and operator problemssuch as excessive or inadequate packing load, excessive inertia,proximity to premature tripping, incorrectly set operating limit andtorque switches, improperly functioning thermal overload devices,inadequate or excessive stem thrust loads, gear train wear, stem damage,and load relaxation. All of the above forms of valve and/or operatordegradation will be apparent from data records obtained from load,current, and continuity devices, which form part of the total analysisand testing hardware of the invention, described in more detail tofollow. Knowledge of the above actual or pending problems will enablethe user to take necessary corrective action prior to actual failure ofthe valve, to perform its intended function. Early corrective actioncan, therefore, lead to improved system reliability, improved safety,lower maintenance, and repair costs.

The user, of the present invention, will have the capability of testingand monitoring the valve and operator performance remotely, which willreduce personnel radiation exposures in nuclear power plants.Furthermore, the present invention will be of great value to otherindustry applications such as chemical or hazardous materialenvironments or even to those applications where accessibility to thosecomponents is restricted.

The purpose of the present invention, when taken as a whole, is toprovide a method by which the general material and operational conditionof a valve and its associated operator can be determined and evaluated.

One object of the present invention is to provide an actual dynamicvalve operator spring pack movement-time trace.

Another object of the invention is to correlate valve stem load tospring pack movement, and therefore provide a valve stem load-timetrace.

Another object of the invention is to provide an operator motorcurrent-time trace that can be correlated with the valve stem loadtrace.

Another object of the invention is to provide a torque and limit switchon/off-time trace that can be correlated with the valve stem load andmotor current traces.

According to one aspect of the invention there is a diagnosticinterrelationship between the calibrated valve stem load-time trace, themotor current-time trace, and the torque and limit switch position-timetrace.

According to another aspect of the invention the interrelationship ofthe stem load-time trace, motor current-time trace, and the torque andlimit switch position-time trace can be used to verify correct valvestem loads for initial valve and operator installations, or futureoperational testing of the valve and operator.

An alternate embodiment of the present invention includes a speciallydesigned spring pack movement device to facilitate mounting of thedevice to the valve operator housing to allow installation and operationof the device in congested areas.

Other objects, features and advantages of the present invention willbecome apparent upon reading and understanding this specification whentaken in conjunction with the accompanying drawings.

A BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: A pictoral, partial view of one embodiment of a valve, valveoperator, and piping system in accordance with the present invention.

FIG. 2: A cut-away view of a valve operator showing the motor, worm,worm gear, and spring pack arrangement in accordance with the presentinvention.

FIG. 3: A cut-away view of a valve operator showing the motor, worm,worm gear, and spring back arrangement, in accordance with the presentinvention, showing an alternate embodiment to that of FIG. 2.

FIG. 4: A cut-away view of a valve analysis and testing system, showingthe valve operator of FIG. 2, with the attached stem load calibrationdevice and spring pack movement device in accordance with the presentinvention.

FIG. 5: A schematic representation of a valve analysis and testingsystem in accordance with the present invention, showing a valveoperator with attached diagnostic devices, recording device, andrecorded function-time parameters.

FIG. 6: A cut-away view, taken along line 6--6 of FIG. 5, showing thespring movement device, and related components, in accordance with thepresent invention.

FIG. 7: A cut-away view, taken along line 7--7 of FIG. 5, showing thespring movement device, and related components, in accordance with thepresent invention.

FIG. 8: An electrical schematic showing of the design of the switchposition indicating circuitry and sub-components, in accordance with thepresent invention.

FIG. 8A: A sample trace from the magnetic coil of the limit/torqueswitch position device, in accordance with the present invention.

FIG. 9: An electrical block diagram showing how the system signals areobtained and processed, in accordance with the present invention.

A DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now in greater detail to the drawings, in which like numeralsrepresent like components throughout the different views, FIG. 1 showsthe environment in which the preferred embodiment of the invention isused. A process pipe 14, having a valve 15, with an attached operator 16is within an operating system with a prescribed flow, pressure, andtemperature. The valve 15 is opened or closed as required for systemcontrol, and is opened or closed by the operator 16. The operator 16 canbe electromechanical, mechanical, pneumatic, or hydraulic.

FIGS. 2 and 3 show two embodiments of operators 16, 16' used in thepresent invention. The components of the two FIGS. 2 and 3 are similaralthough differently arranged. The operators 16,16' are similar tooperator and valve stem arrangements typically used in the art. Themotor 1 drives a worm shaft 2, which in turn drives a worm 3, which inturn drives a worm gear 4, which in turn drives the valve stem 5, toopen or close the valve 15. A reaction device to the actual stem thrustand inertia of the motor and other operator components is shown as acluster of compression springs or spring pack 7 provided at one end ofthe worm shaft 2, as shown in FIGS. 2 and 3. When the valve 15 closes oropens, the valve stem 5 will abruptly stop and even though the currentto the motor 1 is interrupted, the rotational and kinetic energy of thesystem will cause the worm gear 4 to induce additional loads on thevalve stem 5. In order to absorb some of this energy, the spring pack 7is provided and is compressed by the worm shaft 2 as the inertia of thesystem attempts to move the valve stem 5.

FIG. 5 shows a stem load calibration device 17, and a spring packmovement device 8, which are used to calibrate the spring pack 7movement relative to the imposed load on the valve stem 5. Thiscalibration and correlation is accomplished by a simultaneous inducementof a load into the operator through the worm shaft 2, and tracing theactual stem 5 load and spring back 7 movement through the use of acalibrated load cell 9 and linear velocity differential transducer(LVDT) 30.

SPRING PACK MOVEMENT DEVICE 8

The Spring Pack Movement Device 8 is shown in detail in FIGS. 6 and 7.Its function is to monitor both statically and dynamically the linearmotion of the operator spring pack 7. FIGS. 6 and 7 show the significantcomponents and operation of the spring back movement device 8. Withreference to FIGS. 1, 4, 5, 6, and 7, the spring pack movement device 8and attached mounting bracket 21 is bolted directly onto the spring packhousing 35, which is an integral part of the operator 16. The extensionrod 22 is pressed against the spring pack 7 by the tension systemconsisting of the small diameter wire 23, attached to the extension rod22, the LVDT core 24 attached to the wire 23, wire 25, and the spring26. The tension system including the spring 26 force is designed suchthat the rapid movement of a given spring pack 7 does not produceinertia forces in the tension system that would allow separation of theextension rod 22 and spring pack 7. The LVDT core 24 is mounted in acommercially available linear voltage differential transducer 30, whichis supported by bracket 31. The drum wheels 27, 28, and 29 are used, andso located, to convert the translation of the extension rod 22 intoaxial movement of the LVDT core 24, inside the LVDT 30. Thus, the springpack 7 movement is traced electronically and this movement is displayedon an analytical device such as an Oscilloscope 10a (FIG. 5),hereinafter known generally as the recorder 10a.

STEM LOAD CALIBRATION DEVICE 17

The purpose of this the Stem Load Calibration Device 17 is to initiallycorrelate the movement of the spring pack 7 to the actual load beingdelivered to a valve stem 5. Stem load can be calibrated to lineardisplacement of the spring pack 7 since one is merely a reactor to theother. The calibration device 17 is a structure, preferably of steel,comprised of multiple support rods 6 and a drilled flat circular plate20. On the underside of the plate is fastened a calibrated load cell 9,which is a well known device in the state of the art. The calibrationdevice 17 sits above the valve operator body 16. When an extension shaft34 is then placed between the lower surface of the load cell 9 and theupper valve stem 5 surface, a load can be induced on the stem 5 byinputing torque via the worm shaft 2.

CHANNEL SELECTOR AND SIGNAL CONDITIONER DEVICE 10

The purpose of the channel selector and signal conditioner device 10 isas follows:

(Refer to FIG. 5.)

1. Provide a conditioned power supply for the LVDT of the spring packmovement device 8, for load cell 9 and torque/limit switch positionindicating device 18.

2. House the electronic circuitry (see FIG. 8) for the detection of thelimit and torque switch position. This circuit will be discussed in moredetail to follow.

3. Provide the necessary sub-components for switching capabilities toenable the user to output any of the following signals to the datacollection system; spring pack movement, load cell, motor current, andtorque/limit control circuit switch position.

4. Provide input and output connections for an external motor currentmeasuring device 11.

5. Provide local digital readout capabilities for the load cell 9 andspring back movement device 8.

6. Provide a load cell 9 calibration circuit and output signal forverifying proper operation of the recording device 10a.

LIMIT/TORQUE SWITCH POSITION DEVICE 18

The limit/torque switch position device 18 comprises a sensing circuitand associated electronics which are housed in the channel selector andconditioning device 10. As can be seen from the electrical schematicdiagram, FIG. 8, the circuit will provide a varying output to therecording device 10a depending on which of the switches (limit 33, ortorque 32) are closed or opened. It should be noted that if valve 15 isbeing operated, only one of the contacts identified as MC or MO (FIG. 8)will be closed, depending on whether the valve is being opened orclosed. A sample trace from the magnetic coil 45 is shown in FIG. 8A forease of understanding. Note that the variable output shown in the sampletrace is obtained by looping the signal wire from one side of theparallel control circuit around the magnetic coil more times than thesignal wire from the other parallel path. The result of this embodimentof the invention is an output of the recording device 10a, whosemagnitude is reflective of which of the two parallel paths, or both, hasits associated switches opened or closed.

CURRENT MEASURING DEVICE 11

The current measuring device 11 is used to monitor the current draw ofthe valve operator motor 1 during the operation of the valve 15. Thepower required to operate valve 15 can be directly correlated to theactual delivered stem thrust of the operator 16, and thus, correspondingtraces (curves) for the stem load 13 and motor current 12 will beobtained. By initial comparison of the two curves 12 and 13, the usercan subsequently obtain either one of the signature traces 12 or 13, andhave sufficient information on the performance of the valve/operatorassembly. The desirability of the current signature traces 12 lies inthe fact that it is generally easier to obtain than the stem load curve13. The component which is preferably used to obtain the motor currenttrace 12 is a clamp-on ampmeter 11 which is well known to those familiarwith the state of the art. The signal output of the motor currentmeasuring device 11 is sent to the channel selector and conditioningdevice 10 which has been described previously.

RECORDER 10a

The recorder 10a is intended to acquire and store the input data forsubsequent display on a screen, or hardcopy printer, for analysis and/orrecord purposes. Typical recording devices 10a used for the abovepurposes are well known to those familiar with the state of the art.

The interrelationship of the above described components of the preferredembodiment of the valve analysis and testing system of the presentinvention is shown in FIG. 5.

An electrical block diagram of the invention is provided as FIG. 9, toshow how the electrical signals are obtained and processed by each ofcomponent parts, also, referred to as component sub-systems.

Referring to FIG. 5 and having established the valve stem 5 load andspring pack 7 movement relationship and connecting the spring packmovement device 8 to the channel selector and conditioning device 10,the spring pack 7 movement (which is indicative of actual stem load) asa function of time can be recorded as a stem load trace 13 for anyoperation cycle of the valve. In addition, the motor current measuringdevice 11 is given to provide a current trace 12, and can be correlatedto the stem load trace 13 for further operator and valve performanceevaluation, as defined later.

As seen in FIGS. 4 and 5, the valve operator 16 includes a torque switch32 and limit switch 33 (located within the indicated housing, but notseen here), which are connected and function in a manner known in theart. A torque/limit switch position indication device 18 is electricallywired into the torque switch 32 and limit switch 33 control circuit, asshown in FIG. 8. The output from the torque/limit switch position device18 is connected to the recording device 10a, via the channel selectorand conditioning device 10, which in turn provides a switch on-off-timetrace 19, also called torque/limit switch position-time trace 19, forthe duration of the operator cycle.

When the spring pack measuring device 8, motor current measuring device11, and the torque/limit switch position indication device 18 areactivated simultaneously and recordings of each, with reference to thesame operator cycle-time, are obtained the relationship of therecordings provide diagnostic data. To be more specific, since thespring pack 7 movement is calibrated to the valve stem 5 load, thespring pack movement trace is a direct dynamic stem load-timerelationship for an operator cycle. Thus, the spring pack tracecorresponds to actual stem load. As a result of the correlation, thestem load trace 13 is also a spring pack movement trace 13 and will beused interchangeably in subsequently describing the invention. Thecurrent measuring device 11 measures the current required by theoperator motor to deliver the stem load and, therefore, the current-timetrace 12 is also a record of the valve stem load-time relationship. Inaddition, the torque/limit switch indicating device 18 provides a switchposition indication for the torque and limit switches 32 and 33,therefore the torque/limit switch position-time trace 19 provides adirect indication of the torque and limit switch timing relationship.Most important is that the torque and limit switch "off" indication canbe compared to the stem load trace 13 to establish the additional stemloads delivered to the stem by the inertia of the motor and operator 16,after the torque and limit switches 32 and 33, have interrupted thecurrent to the motor. It is recognized that the stem load trace 13 is adirect record of the dynamic valve stem load during the valve operatorcycle, and therefore provides confirmation of the actual load imposed onthe valve stem 5. If the recorded stem load is less than, or greaterthan, that required for proper valve operation, the traces 12, 13 and15, are compared and the comparisons are used to readjust the torqueswitch 32 and/or limit 33 switch settings, and therefore the stem loadto within required limits.

Further a spring pack movement or stem load trace 13, current trace 12,and switch position trace 19, generated from a properly functioningvalve and operator combination, can be used as a data base forcomparison of subsequent spring pack movement, current and switchposition indication traces for purposes of verification of performance,or as a means of detecting improper functioning components of the valve15 and operator 16.

In preferred embodiments, the process of comparison and analysis of thedata is accomplished through the use of computer data bases andspecialized programs which calculate and compare critical valve 15 andoperator 16 parameters. This historical comparison identifies to theuser a slowly degrading condition, which heretofore could not be readilydetected between sequential test frequencies.

Typical valve and operator parameters which are determined and comparedfrom the dynamic traces 12, 13 and 19 are as follows:

A. Stem load versus spring pack 7 deflection. Correlation of these twoparameters provides the user with a known stem load for a given,subsequently obtained, spring pack movement.

B. Valve packing load changes.

C. Starting stem load to initially move the valve from its closed oropen position, commonly known in the state of the art as hammer blow.

D. Total stem load, which is the final observed stem load at the end ofa given valve cycle.

E. Available stem load to seat a valve. This load is the differencebetween the packing and and total stem load.

F. Stem load at which the torque or limit switches actuate. Thisprovides information on the overall operational set-up of a valve andoperator control circuitry.

G. Total time for the valve to open or close.

H. General condition of the operator mechanical gearing and stem, byanalysis of the valve mid-cycle stem load trace 13.

I. Average motor current requirements, which if it changes, can providean indication of degrading valve performance.

An example of a computer program, which is part of the invention toperform the above analytical manipulations, is shown following:

This is an example computer program for analysis of motor operated valvespring pack 7 movement, motor current (at current measuring device 11)and torque/limit switch 32 and 33 activation. This program is writtenfor the Norland 3000 DMX computer.

    ______________________________________                                        Program listing:                                                              ______________________________________                                        1.         Display B C C'D E'RO DPLY                                          2.         O > B                                                              3.         O > C                                                              4.         O > C'                                                             5.         O > D                                                              6.         O > E'                                                             7.         O > RO                                                             8.         PAUS                                                               9.         PAUS                                                               10.        O IF > RI                                                          11.        D DISK 101                                                         12.        D DISk 102                                                         13.        D DISK 103                                                         14.        D DISK 104                                                         15.        D DISK 105                                                         16.        D DISK 106                                                         17.        D DISK 107                                                         18.        D DISK 108                                                         19.        D DISK 109                                                         20.        D DISK 110                                                         21.        D DISK 111                                                         22.        D DISK 112                                                         23.        D DISK 113                                                         24.        D DISK 114                                                         25.        END                                                                26.        PAUS                                                               27.        PAUS                                                               28.        DPLY A > DISK 104                                                  29.        DISK 104 LBL DATE LBL                                              30.        DPLY A' > DISK 105                                                 31.        DISK 105 LBL TIME LBL                                              32.        DPLY D' > DISK 111                                                 33.        DISK 111 LBL LOAD CONV LBL                                         34.        PAUS                                                               35.        PAUS                                                               36.        DPLY Q1 > DISK 101                                                 37.        DISK 101 LBL Q1 CURVE LBL                                          38.        DPLY Q2 > DISK 102                                                 39.        DISK 102 LBL Q2 CURVE LBL                                          40.        DPLY Q3 > DISK 103                                                 41.        DISK 103 LBL Q2 CURVE LBL                                          42.        PAUS                                                               43.        PAUS                                                               44.        RMS > C'                                                           45.        COOR                                                               46.        C' > R8                                                            47.        O IF > V                                                           48.        O IF > V'                                                          49.        C' * -1 > C'                                                       50.        GOTO 61                                                            51.        END                                                                52.        GOTO 119                                                           53.        END                                                                54.        O IF > V'                                                          55.        O IF > V                                                           56.        C' * -1 > C'                                                       57.        GOTO 61                                                            58.        END                                                                59.        GOTO 119                                                           60.        END                                                                61.        PAUS                                                               62.        PAUS                                                               63.        COOR                                                               H > D      H'                                                                 65.        PAUS                                                               66.        PAUS                                                               67.        COOR                                                               68.        C'- V > E                                                          69.        E * D' > E                                                         70.        PAUS                                                               71.        PAUS                                                               72.        COOR                                                               V > C      V'                                                                 74.        C * D' > C                                                         75.        PAUS                                                               76.        PAUS                                                               77.        RMS > B'                                                           78.        B' > R9                                                            79.        COOR                                                               80.        O IF > V                                                           81.        O IF > V'                                                          82.        B' * -1 > B'                                                       83.        GOTO 94                                                            84.        END                                                                85.        GOTO 119                                                           86.        END                                                                87.        O IF > V'                                                          88.        O IF > V                                                           89.        B' * -1 > B'                                                       90.        GOTO 94                                                            91.        END                                                                92.        GOTO 119                                                           93.        END                                                                94.        B' * D' > B                                                        95.        R9 - R8 > RO                                                       96.        RO * D' > RO                                                       97.        PAUS                                                               98.        PAUS                                                               99.        COOR                                                               V > E'     C'                                                                 101.       E' * D' > E'                                                       102.       C' * D' > C'                                                       103.       DPLY B > DISK 106                                                  104.       DISK 106 LABL RUNNG UBS LABL                                       105.       DPLY B' > DISK 107                                                 106.       DISK 107 LABL RUNNG V LABL                                         107.       DPLY C > DISK 108                                                  108.       DISK 108 LABL AVA THRST LABL                                       109.       DPLY C' > DISK 109                                                 110.       DISK 109 LABL PRE HB RMS LABL                                      111.       DPLY D > DISK 110                                                  112.       DISK 110 LABL TIME O/C LABL                                        113.       DPLY E > DISK 112                                                  114.       DISK 112 LABL PKHB/RMS LABL                                        115.       DPLY E' > DISK 113                                                 116.       DISK 113 LABL TTL THRST LABL                                       117.       DPLY RO > DISK 114                                                 118.       DISK 114 LABL DKNG LD LABL                                         119.       END                                                                ______________________________________                                    

Although only the preferred embodiment of the invention has beendescribed, it is evident that the invention will find uses other thanelectric motor operated valves. For example, the invention is useful forverifying correct operation of manual, hydraulic, and pneumatic actuatedvalves.

Whereas, this invention has been described in detail with particularreference to preferred embodiments thereof, it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention, as described before and as defined in the appendedclaims.

What is claimed is as follows:
 1. Method for determining and evaluatingthe general material and operational condition of a valve and/or anassociated operator thereof said method comprising:monitoring a drivesystem for said operator; providing a dynamic valve operator spring packmovement/time trace; correlating valve stem load to spring pack movementto provide a valve stem load/time trace; providing a motor current/timetrace; correlating the motor current/time trace with the valve stemload/time trace; providing a torque and limit switch on-off/time trace;correlating the switch on-off/time trace with the valve stem load/timetrace and the motor current/time trace; and diagnosing the correlatedtraces to evaluate the condition of the valve and/or valve operator. 2.Method of claim 1 wherein the step of continously monitoring theoperator drive system is accomplished from a remote site isolated fromthe location of the valve and operator.
 3. Method of providing ahistorical comparison of the general operating condition of a valveand/or valve operator having a motor driven worm shaft, which drives aworm which in turn drives a worm gear, which in turn drives a valve stemto open and close a valve attached to the valve stem, and having aspring pack compressed by movement of the worm, said method ofcomprising the steps of:correlating spring pack movement to valve stemload; measuring spring pack movement over given time to develop acorrelated stem load/time trace; measuring motor current draw over thesame given time to develop a motor current/time trace; detecting switchpositions of respective torque switches and limit switches over the samegiven time to develop a switch position/time trace; analyzing andcomparing the stem load/time trace, motor current/time trace, and switchposition/time trace to evaluate the relative condition of the valveand/or valve operator.
 4. Method of claim 3, wherein the steps ofmeasuring, detecting, and analyzing and comparing are accomplished froma remote site isolated from the location of the valve and operator. 5.Method for determining and evaluating the general material andoperational condition of a valve and/or an associated operator thereof,said method comprising:monitoring a drive system for said operator overa period of time by thereduring measuring and recording valve stem load,a spring pack reaction to the worm, an electrical operatingcharacteristic of the motor, and torque and/or limit switch position;providing a first parameter/time trace in which the parameter is one ofeither valve stem load or spring pack movement or motor current ortorque and limit switch position; providing a second parameter/timetrace in which the parameter is one of the aforestated; correlating thefirst parameter/time trace with the second parameter/time trace; anddiagnosing the correlated traces to evaluate the condition of the valveand/or valve operator.
 6. Method of claim 5, further comprising thesteps of:providing a third parameter/time trace in which the parameteris one of the aforestated; and correlating the first, second and thirdparameter/time traces with one another.
 7. Method for determining andevaluating the general material and operational condition of a valveand/or an associated operator thereof, said method comprising the stepsof:monitoring a drive system for said operator over a period of time;providing a dynamic valve operator spring pack movement/time trace;correlating valve stem load to spring pack movement to provide a valvestem load/time trace; and diagnosing the load/time trace to evaluate thecondition of the valve and/or valve operator.
 8. Method of claim 7,further comprising the steps of:providing a torque and limit switchon-off/time trace; correlating the switch on-off/time trace with thestem load/time trace; and diagnosing the correlated traces to evaluatethe condition of the valve and/or valve operator.
 9. Method of claim 7,further comprising the steps of:providing a motor current/time trace;correlating the current/time trace to the stem load/time trace; anddiagnosing the correlated traces to evaluate the condition of the valveand/or valve operator.
 10. Method for determining and evaluating thegeneral material and operational condition of a valve and/or anassociated operator thereof, having a driven worm shaft, which drives aworm which in turn drives a worm gear, which in turn drives a valve stemto open and close a valve attached to the valve stem, and having aspring pack compressed by movement of the worm, said method, comprisingthe steps of:operating the valve operator to drive the valve stem;inducing test loads into the valve operator by imposed resistance tomovement of the valve stem; measuring the test loads induced into thevalve operator; measuring reaction of the spring pack to the test loadsinduced into the valve operator; correlating the measured test loads tothe measured reaction of the spring pack to the test loads, andcalibrating the spring pack reaction relative to the measured loads;operating the valve operator over a monitored period of time, wherebyunmeasured operating loads are induced into the valve operator byresistance to valve stem movement during valve-in-use conditions;measuring reaction of the spring pack during the monitored period oftime; and deriving a representation of the unmeasured operating loads inresponse to measuring of the spring pack reaction.
 11. Method of claim10, wherein the step of inducing test loads into the valve operatorcomprises the steps of:blocking the lineal movement of the valve stem;and continuing to drive the valve stem by operation of the valveoperator; whereby forces exerted by the worm shaft progressivelyincrease.
 12. Method of claim 10, wherein the step of measuring the testloads comprises the steps of measuring the resistance forces imposed onthe valve stem.
 13. Method of claim 10, wherein the spring pack reactionmeasured and correlated is the lineal motion of the spring pack as thespring pack is compressed by the worm.
 14. Method of claim 10, whereinthe step of inducing test loads into the valve operator comprises thestep of inducing test loads on the worm of the valve operator byimposing resistance to movement of the valve stem.
 15. Method of claim10, wherein the step of deriving a representation of the unmeasuredoperating loads comprises the step of deriving a time related trace ofthe unmeasured operating loads in response to measuring of the springpack reaction, and further comprising the step of diagnosing the timerelated trace of the unmeasured operating loads to evaluate thecondition of the valve and/or valve operator.
 16. Method for determiningand evaluating the general material and operational condition of a valveand/or an associated operator thereof, having a driven worm shaft, whichdrives a worm which in turn drives a worm gear, which in turn drives avalve stem to open and close a valve attached to the valve stem, andhaving a spring pack compressed by movement of the worm, said methodcomprising the steps of:imposing a test load on the valve stem;measuring the test load imposed on the valve stem; observing a wormreaction parameter in response to the test load imposed on the valvestem; measuring the worm reaction parameter; calibrating the wormreaction parameter relative to the imposed test load on the valve stem;operating the valve operator over a monitored period of time, wherebyunmeasured stem loads are experienced affecting the valve stem;measuring the worm reaction parameter over the monitored period of time;deriving a time related trace of unmeasured stem loads over themonitored period of time in response to the measuring of the wormreaction parameter; and diagnosing the time related trace of the stemloads to evaluate the condition of the valve and/or valve operator. 17.Method of claim 16, wherein the worm reaction parameter observed,measured and calibrated is a displacement parameter relating to linealmovement of the worm; and the step of measuring the worm reactionparameter includes the step of measuring the linear motion of theoperator spring pack over the monitored period of time.
 18. Method ofclaim 17, wherein the step of deriving a time related trace of theunmeasured stem loads includes the steps of:providing a time relatedtrace of the spring pack motion over the monitored period of time; andcorrelating the spring pack motion over the monitored period to thecalibrated spring pack motion and test loads to derive a time relatedtrace of stem loads over the monitored period.
 19. Method of claim 16,further comprising the steps of:measuring operator motor current drawover the monitored period of time; providing a time related trace of themotor current over the monitored period of time; correlating the timerelated trace of the motor current to the time related trace of the stemloads; and diagnosing the correlated traces to evaluate the condition ofthe valve and/or valve operator.
 20. Method of claim 16, furthercomprising the steps of:measuring the switch positions of the respectiveoperator torque switches and limit switches over the monitored period oftime; providing a time related trace of the switch positions over themonitored period of time; comparing and analyzing the time related traceof the switch positions to the time related trace of the stem loads toevaluate the condition of the valve and/or valve operator.
 21. Methodfor determining and evaluating the general, material and operationalcondition of a valve and/or an associated operator thereof having anoperator drive system which drives a valve stem to open and close thevalve and also including a spring pack compressible by the drive system,said method comprising the steps of:monitoring the operator drive systemover a period of time; providing a dynamic time related trace of thevalve operator spring pack action; correlating valve stem load to springpack action; deriving a time related trace of unmeasured stem loads overthe given period of time; and diagnosing the time related trace of thestem loads to evaluate the condition of the valve and/or valve operator.22. Method of claim 21, wherein the step of providing a dynamic timerelated trace of the valve operator spring pack action comprises thesteps of:measuring deflection of the operator spring pack over theperiod of time, as the spring pack is compressed by a worm included aspart of the drive system; and providing a time related trace of thespring pack deflection.
 23. Method of claim 21, further comprising thesteps of:providing a torque and limit switch on-off/time trace;correlating the switch on-off/time trace with the stem load/time trace;and diagnosing the correlated traces to evaluate the condition of thevalve and/or valve operator.
 24. Method of claim 21, further comprisingthe steps of:providing a motor current/time trace; correlating thecurrent/time trace to the stem load/time trace; and diagnosing thecorrelated traces to evaluate the condition of the valve and/or valveoperator.
 25. Method for determining and evaluating the general materialand operational condition of a valve and/or an associated operatorthereof, having a driven worm shaft, which drives a worm which in turndrives a worm gear, which in turn drives a valve stem to open and closea valve attached to the valve stem, and having a spring pack compressedby movement of the worm, said method comprising the steps of:operatingthe valve operator to drive the valve stem over a period of time;developing loads within the valve operator; measuring the developedloads within the valve operator; measuring displacement of the springpack in reaction to the developed loads; calibrating the spring packdisplacement to the developed loads; deriving a time related history ofunmeasured loads in response to measuring the spring pack deflection.26. Method of claim 25, wherein the step of developing loads within thevalve operator includes the step of imposing resistance to movement ofthe valve stem.
 27. Method of claim 25, wherein the step of developingloads within the valve operator includes developing loads on the worm.28. Method of claim 25, further comprising the steps of:recording a timerelated trace of the stem load; and diagnosing the time related trace ofthe stem load to evaluate the condition of the valve and/or valveoperator.
 29. Method for determining and evaluating the general materialand operational condition of a valve and/or an associated operatorthereof, having a driven worm shaft, which drives a worm which in turndrives a worm gear, which in turn drives a valve stem to open and closea valve attached to the valve stem, and having a spring back compressedby movement of the worm, said method comprising the steps of:monitoringthe operation of the valve operator over a period of time; measuringdisplacement of the spring pack during the operation of the valveoperator over the period of time; providing a time related trace of thespring pack displacement; and diagnosing the time related trace of thespring pack movement to evaluate the condition of the valve and/or valveoperator.
 30. Method for determining and evaluating the general materialand operational condition of a valve and/or an associated operatorthereof, having a driven worm shaft, which drives a worm which in turndrives a worm gear, which in turn drives a valve stem to open and closea valve attached to the valve stem, and having a spring pack compressedby action of the worm, said method comprising the steps of:monitoringthe operator drive system over a period of time by thereduringmonitoring and recording reaction of the spring pack to action of theworm; providing a first parameter/time trace in which the parameter isspring pack reaction to action of the worm; providing a secondparameter/time trace in which the parameter is one of either valve stemload, or motor current, or torque and limit switch positions;correlating the first parameter/time trace with the secondparameter/time trace; and diagnosing the correlated traces to evaluatethe condition of the valve and/or valve operator.
 31. Method of claim 30further comprising the steps of:providing a third parameter/time tracein which the parameter is one of either valve stem load, or motorcurrent, or torque and limit switch positions; and correlating thefirst, second and third parameter/time traces with one another. 32.Method of claim 30, wherein the spring pack reaction which is monitored,recorded and traced with respect to time is the movement of the springpack as the spring pack is compressed by action of the worm.